The present invention relates to bicycle free wheels and relates more specifically to the production of exterior sprocket support rings for such free wheels.
Exterior sprocket support rings for multi-speed bicycle free wheels are components which support the various sprockets on which the transmission chain will resolve as required by the cyclist when the latter wishes to adapt his effort and his speed to the contour of the road which he is travelling.
In a first known form, these rings are thick tubular components obtained by machining forged or stamped blanks, or by simple machining. They receive sprockets to which they are fixed by means such as threading and/or keying. In the interior part of these rings are provided two ball races for rows of balls, obtained by stamping, machining and/or rolling, and ratchets, obtained by forging, slotting or broaching.
According to a second known form, these rings can themselves be toothed on the exterior and hence require the presence of a reduced number of sprockets for the same number of gears.
Finally, in a third known form, described in published FR Patent Application No. 2,584,639, belonging to the Applicant, there is no longer a sprocket support ring in the strict sence, but a welded assembly of different sprockets, each of whose bores possesses a toothing, and whose extreme sprockets possess rolling surfaces, which makes it possible to create the two ball races for the rows of balls and the ratchets.
The sprocket support rings produced according to the first two known forms require the utilization of powerful equipment, consuming large quantities of energy, entailing substantial wastage of material during the machining stages and hence resulting in the production of articles whose retail price is relatively high.
The group of sprockets assembled in accordance with the abovementioned patent application, and replacing the ring, results in the utilization of less powerful equipment and in reduced wastage of material, but makes it necessary to have available numerous sprocket models (and tooling to create them) since the sprockets vary both in respect of their number of teeth and in respect of their profile, which varies in accordance with the position they occupy.